Association of the catechol-O-methyltransferase polymorphism with methylphenidate response in a classroom setting in children with attention-deficit hyperactivity disorder.

It has been postulated that the prefrontal cortex plays a key role in attention-deficit hyperactivity disorder (ADHD). The catechol-O-methyltransferase (COMT) enzyme degrades synaptic catecholamines and plays a specific role in the catabolism of prefrontal cortex dopamine. We investigated the association between the COMT valine (Val) 108/158 methionine (Met) polymorphism and the response to treatment with methylphenidate (MPH) in children with ADHD. This study included 124 children with ADHD in South Korea. Those patients who had an improvement after 8 weeks of treatment greater than or equal to 50% compared with the baseline ADHD rating scale scores before treatment were considered to be the 'good response' group. After performing genotyping for COMT, we examined the correlation of the COMT polymorphism with response to treatment with MPH using the chi test. We found that whereas 62.5% of the patients showing a good response to MPH treatment had the Val/Val genotype, 41.7 and 11.7% of the patients showing a poor response to MPH treatment as assessed by their teachers had the Val/Met and Met/Met genotypes (chi=6.58, d.f.=2, P=0.035). Our findings provide evidence of an association between the COMT genotype and MPH response as assessed by the teachers of children with ADHD.